I use t-slot most of the time

[Mike Everman]

This is a forum for me! Just thought I'd start it off with something.
My favorite is Bosch, usually dead straight. Love those German products, though not the cheapest, it is the best.

The 45mm series is good for mounting 20mm bearing rails, and the 30mm is good for 15mm rails, but not many choices on section.

If you do a search for servobelt, you'll see many examples of what I mean.

[Swede]

Is this a new sub-forum? Maybe I missed it before.

I agree that the Bosch "heavy" sections are superb. It's hard to describe it until you actually use these things, but the full-length T-slots allow for some amazing flexibility when it comes time to put things together, and they are far more rigid than one might think.

A few years ago, I finished a mill project using mostly Bosch elements, along with quite a bit of plate. While the extrusions are reasonably straight, for critical portions, like rail attachments, I think it is best to take a face mill to one side which creates a dead flat and true surface.







The solid steel T-nut sections are (by far) the best for attaching rails. Rather than 6 or 8 separate T-nuts, you have one individual long steel nut securing the rail, without any stress points created. But the "swivel-in-place" T-nuts are hard to beat for light-duty attachments and such.



The other beauty of these systems is that you can add attachments later in moments. For example, let's say you want to add a bracket for a mist cooling system. Normally you'd have to drill and tap a column, but with the t-slot sections, you make your bracket and on it goes using a swiveling t-nut. And you can reposition or remove it in moments.

The same applies to simple things like limit switches:



It's great stuff!

[gearsoup]

What's the average price of these items? Weighing the costs of getting a large aluminum plate for my machine table, or perhaps going with something like this.

[Swede]

What's the average price of these items? Weighing the costs of getting a large aluminum plate for my machine table, or perhaps going with something like this.

I would not use these for a table unless you can accept a flatness that is not perfect. I don't know the tolerances, but if you clamped these together to form a table, I'm guessing it'd have variations on the order of 0.020" / 0.5mm over 1/2 meter. Again, those are just guesses, it may be better, or worse, but it won't be flat. But maybe your application can deal with that, only you know the answer.

One option which I have used with good effect is to attach a piece (heavier is better) of MIC-6 aluminum jig/fixture plate to supporting sections of extrusion. MIC-6 plate is accurate, and the combination of the two produces an outstanding machine member; light, stiff, accurate.

Prices - don't know, they can be expensive, but no worse that comparable solid stock. Sections can be bought used or surplus at great savings.

[nickswimsfast]

Swede, given that you have used your machine with extrusions for this long, have you had any problems vibrations? For example, the t-nuts loosening with time? Or mechanical creep or fatigue on the extrusions themselves?


I presume you are from 5-bears? I have been very carefully studying your machine's design, as I am working on emulating similar elements in my own first CNC machine. Thank you for such a detailed and explanatory build, it has been a tremendous help.

[Swede]

Hi Nick, I'm the 5 Bears guy. I've been humbled by the number of people who followed the site over the years, and I hope to get it going once more.

The design and concept isn't mine, it's been around for a while. I borrowed heavily from a nice eBay mill that used steppers and a piece of aluminum extrusion for the table. I wanted to take the basic design and try to improve on it with an iron table, good ball screws and rails, and with overall stiffening by using plate to sandwich and also to protect the LM hardware.

My mill is servo and the motion hardware is good stuff, so vibrations have not caused any issues at all. The cap screws tighten such that when you loosen them, it has that satisfying "snap" as they initially loosen, which means that the interface is tight without slop or deformation. I'm not sure I'm describing it well.

I used almost exclusively the steel t-nut strip stock, in long lengths, rather than individual t-nuts. I think this is important, and the stock is not all that expensive.

If I were to do another mill, I'd absolutely use the much heavier section shown here for the Z, with perhaps added stiffening plate.



Aluminum does not deaden vibrations as well as CI, but it seems to work fine at the scales one would typically see these used for.

[nickswimsfast]

I understand what you mean by the satisfying "snap." I was asking due to the potential need for thread-lock on a machine such as yours. I believe that answers the question.

When I complete my machine build, I may try to install sand-epoxy composite inside of the 80-20 cavities. That should raise the natural frequency of the machine, and increase the damping of the overall machine. Alternatively, for a simple mod, you could simply pour sand into those cavities and cap the ends to contain it. Those open cavities just beg to be filled with something. This could be a good addition to any T-Slot machines that are not going to be moved much. Something to think about

I just took a vibrations class for my mechanical engineering degree last term. So it has been fresh on the mind. For more fun I may even analyze the determine the natural frequency of the machine so I know what RPM's to avoid, but that is a long way out.

[voltsandbolts]

T-Slot CNC building

This must be a new area, but I’ll be checking in here often. I am interested in building a small T-slot based machine for routing PC-boards. Something in the 12” x 12” size. I hope I can pick up some good ideas here.

Later,
Rob.

[Swede]

You'll like the system, Rob. It is perfect for PC board routing. I can picture some very east to set up clamps and such for the PC boards that take full advantage of the T-slots. And since most boards are 18" or less, you can have a nice, compact machine.

The extrusions will have the rigidity. All you need to worry about is the precision of your motion hardware, depending upon the size of your traces. That, and a very high speed spindle capable of clean cuts in that nasty resin they use, which eats carbide for lunch. The good part is that routing bits are all over eBay, pretty cheap.

[tig-racer]

nice use a your mill and T-slot. i need to find someone locally with skills like yours. thanks for posting info about your use of T-slot.

[Biermann]

If I were to do another mill, I'd absolutely use the much heavier section shown here for the Z, with perhaps added stiffening plate.



Aluminum does not deaden vibrations as well as CI, but it seems to work fine at the scales one would typically see these used for.

Hi Swede,

Could you tell me the manufacturer of that heavier extrusion. What would you estimate the max size wood and light aluminum gantry it could support.

Will have to check out your website.

Thanks

[drivercl]

Gents,
I've found this Bosch Rexroth framing catalog. Has anyone bought from this site ever?

Cheers

Aluminum Framing Catalog


45mm series here:
http://www13.boschrexroth-us.com/Fra...age%202-26.pdf